The present invention relates to a new and distinct perennial Blue Flax Lilly variety of Dianella caerulea, which has been given the varietal denomination of ‘DBB03’. The market class for ‘DBB03’ is that of an ornamental grass-like plant. ‘DBB03’ is intended for use in landscaping and as a decorative grass-like plant.
An application for plant breeders' rights for variety ‘DBB03’ has been filed with the Australian Plant Breeders' Rights Office, and was first gazetted in the Plant Varieties Journal in October 2003 under Application No. 2003/291.
Parentage: The Dianella caerulea variety ‘DBB03’ was first discovered in October 1996 in an Australian nursery in Clarendon, New South Wales after an extensive breeding program. The parent plant, ‘Sydney Ecotype’ (unpatented), is characterized by a tall plant height, a medium plant density, medium length aerial stems and a yellow-green leaf colour.
In 1995, Dianella species were grown together in an open bed covering approximately 250 square meters of area. They were grown in groups of species and ecotypes including Dianella caerulea collected from the Sydney area (Dianella caerulea ‘Sydney Ecotype’), and other regions. The other Dianella species present were longifolia, revoluta and tasmanica. The plants were open pollinated with possible assisted pollination from general shaking of flower stems onto each other.
Seeds were collected and sown from the ‘Sydney Ecotype’ plants in December 1995. Approximately 30,000 plants were grown. In October 1996, using the selection criteria of bluish leaf colour, compact habit and absence of aerial stems (canes), a single plant was identified as having these characteristics. This plant was selected, potted into a 140 mm pot for further evaluation, and named ‘DBB03’.
The female parent of ‘DBB03’ was Dianella caerulea ‘Sydney Ecotype’, and ‘DBB03’ has been identified as a Dianella caerulea; however, it is noted that ‘DBB03’ has a similar colour and shares several similar growth habits with some of the Dianella longifolia that were used in the open pollination breeding program. For these reasons, it is possible that the male parent of ‘DBB03’ was a Dianella longifolia. 
Asexual reproduction. ‘DBB03’ was first asexually propagated by vegetative division in April 1997 in the state of New South Wales, Australia. ‘DBB03’ was asexually reproduced again during November 1997 and April 1998 and confirmed to be stable in character. The distinctive characteristics of the inventive variety, ‘DBB03’, have remained stable and true to type from generation to generation through successive cycles of asexual reproduction including vegetative division and micropropagation.